|In 1969, large numbers of North Vietnamese troops entered Cambodia. In March 1970, the Cambodian government requested their removal. Premier Lon Nol took control of the government while Prince Sihanouk was in Peking (March 18th) and pledged to force the removal of the Vietnamese troops. Initially, the Vietnamese agreed to withdraw, but then announced their support for Sihanouk who had promised to fight the new government.
On April 30th, President Nixon announced that U.S. troops would join with South Vietnamese troops to invade the border area of Cambodia and eliminate Communist sanctuaries. He also pledged that all U.S. troops would be out by the end of June. Meanwhile, Communist forces advanced on Pnom Penh.